Prestretch forming fixture for drawing die press



Dec. 10, 1963 P. F. MAIZE 3, 07

PRESTRETCH FORMING FIXTURE FOR DRAWING DIE PRESS Filed Dec. 19. 1960 5Sheets-Sheet 1 PAUL /T MA/ZE BY r y Dec. 10, 1963 P. F. MAlZE I3,113,607

PRESTRETCH FORMING FIXTURE FOR DRAWING DIE PRESS Filed Dec. 19, 1960 5Sheets-Sheet 2 PAUL M/I/ZE BY W ATTORNEY Dec. 10, 1963 P. F. MAIZE 3, 7

PRESTRETCH FORMING FIXTURE FOR DRAWING DIE PRESS Filed Dec. 19. 1960 sSheets-Sheet s Fzy J? PAUL FT MA /Z 4 rme/vi K P. F. MAIZE Dec. 10, 1963PRESTRETCH FORMING FIXTURE FOR DRAWING DIE PRESS Filed Dec. 19, 1960 5Sheets-Sheet 4 INVENTOR. PAUL MA/ZE Dec. 10, 1963 P. F. MAIZE 3,113,607

PRESTRETCH FORMING FIXTURE FOR DRAWING DIE PRESS Filed Dec. 19,' 1960 5Sheets-Sheet 5 INVENTOR. PA UL E M/l/ZE BY q w- ATTOE/VEK Unite Thisinvention relates to a prestretch die drawing fixture for drawing diepresses by which sheet and strip metal stock can be prestretched bytensioning it into a range above its elastic limit while it is disposedbetween the open drawing dies of the press and, while it is heldprestretched under tension by the fixture, drawn to the shape of the diecavity by closure of the drawing dies by the press, in accordance withthe inventions of Cyril 3'. Bath, disclosed in 11.8. Patent No.2,961,028, issued November 22, 1969, and entitled Method and Apparatusfor Combined Stretch and Die Forming of Metal Stock.

More specifically, the present invention relates to a fixture which maybe used in conventional drawing die presses for performing some of themethods described in said above patent.

As therein more fully described, many advantages are obtained bypreconditioning metal stock preparatory to drawing it in dies by placingit under tension in a range above its elastic limit unidirnensionallyand, while it is so tensioned, forming it by drawing it in forming dieswhile leaving the lateral margins which extend along the diniensionbeing tensioned free to be pulled into the dies transversely of theirlength during the die drawing operation.

A number of the advantages described in the above identified patent canbe obtained by mounting the present fixture on the die bed of aconventional drawing die press.

Another advantage obtainable by the method and apparatus of the priorpatent and obtainable by the present fixture, is the elimination ofexpensive and bulky holddown devices for the two margins of the stockwhich are not gripped by the tensioning means, with a consequent largesaving in the amount of stock required to form an article.

Additional advantages reside in the fact that less expensive drawingdies can be used when the die drawing is combined with the presentfixture, inasmuch as the unit pressure required for drawing of the stockwhile it is tensioned in a range above its elastic limit and in theabsence of the usual marginal hold-down devices is much less than thatrequired in conventional press drawing.

Various specific objects of the invention will become apparent from thefollowing description wherein reference is made to the drawings, inwhich:

FIG. 1 is an isometric view of a conventional press with drawing diesand the fixture of the present invention installed therein;

FIG. 2 is an enlarged top plan view of the fixture, part thereof beingshown in section for clearness in illustration;

FIG. 3 is a vertical cross sectional view taken on the lines 33 in FIG.2;

PEG. 4 is a fragmentary front elevation, partly in vertical longitudinalsection, showing the relation of the parts of the structure when thedies are in closed posiion, and taken as indicated by the line 4-4 inFIG. 2; and

FIG. 5 is a fragmentary front elevation similar to H6. 4-, showing thestructure when the dies are in open position.

Referring to the drawings, the press comprises a conventional frame 1having a bed 2 and a power driven ram 3 which is guided by the uprightframe members 4 for cooperation with the bed. A conventional drawing die5 is mounted on the ram and a complementary drawing die 6 is mounted onthe bed 2. Also, conventional die States Patent 0 3,,ll3,67 PatentedDec. ll), 1963 cushions 7, with plates 7a, are mounted in the pressbeneath the bed 2 and are yieldably urged upwardly by a suitableresilient pressure means, such as the piston and cylinder assemblages 8to which air under pressure is supplied from a suitable source, such asa compressed air tank 9. The press described is a conventional type ofdie drawing press and is readily available on the market.

As mentioned in the objects, it is desirable to provide a fixture bywhich a stock can be stretched into a range above its elastic limitwhile disposed between the dies while the dies are in open position. Forthis purpose, fixtures indicated generally at it), and with which thepresent invention are particularly concerned, are provided.

For convenience in description, the press is described as one which isupright and in which the ram '3 moves vertically toward and away from ahorizontal upwardly facing bed 2. The words vertically and horizontallyand the like, as used in describing certain parts, are merely forconvenience in showing the positions of the parts relative to eachother. Such words are not used in their absolute sense as, obviously,the press with the fixtures thereon could be disposed on its sidewithout changing the functioning essentially.

Referring specifically to the fixtures 10, two such fixtures areprovided. These fixtures are secured in fixed position on the bed 2, oneat one end of the die 6 and the other at the other end. Since thefixtures are the same in form and function, one only will be describedin detail. it is to be noted, however, that with two fixtures, one canbe used to grip one end of the stock for applying tension thereto whilethe other grips the other end of the stock and is locked so as to holdthe end it grips in fixed position in the tensioning dimension. On theother hand, if desired, both of the devices may be operated to applytension to the stock by concurrently operating their tensioning means.Whether both are used concurrently for applying tension, or one is usedas a holding means while the other is operated to apply tension, dependsupon the particular type of work being done and the shape of the dies 5and 6.

It is desirable to place the stock under tension preparatory to itsengagement by the dies 5 and 6, and for this purpose the tensioningmeans must be arranged at a particular level, usually above the upperface of the die 6 so that the stock is free from contact with eitherdie, but disposed therebetween, while being tensioned.

For this purpose, each fixture 10 comprises a rigid frame 11 which isadapted to be mounted in fixed position on the bed of the press. Mountedin the frame 11 for ver tical reciprocation is an elevator 12 comprisingan upper frame member -13 and a bottom frame member 14 with suitableside members l5 disposed therebetween and permanently secured theretoand binding them together. The elevator 7.2 is adapted to be lifted andlowered relative to the frame 11 and bed 2. For this purpose, it isprovided along its sides with suitable wear pads 15 which are connectedto the side members 15 and bear against slide surfaces on the inner sidefaces of the frames 11.

The frames ll, at their ends, have inwardly directed rigid portions 17which are adapted to engage the ends of the elevator 12 near their sidesso as to constrain the frame 12- in fixed position endwise of the frame11 and in a direction toward and away from the dies. Suitable Wear pads18 are provided on the portions 17 of the stationary frame andcorresponding 'wear pads l? are provided on the ends of the elevator 12.By virtue of these frame portions 17, the wear pads 18 and 19, and thelateral inner surfaces of the frame ll engaging the wear pads 16, theelevator is guided for lineal movement in a generally upright path whileconstrained from movement laterally or endwise.

The elevator is adapted to be supported for vertical movement by thestationary frame 11 on the die bed in a position to be engaged bysuitable lift rods which extend through conventional openings in the bed2. Beneath the bed, the lift rods engage the upper faces of the plates7a which are supported yieldably by the piston and cylinder assemblagesof the die cushions '7, heretofore mentioned.

This arrangement provides a die cushioning means which is a resilientmeans and acts through the rod 28 for yieldably holding the elevator inpredetermined raise position above the bed 2.

Mounted on the ram 3 for movement therewith are pusher posts 21 whichare adapted to engage the upper member 13 of the elevator 12 and pushthe elevator downwardly against the yieldable resistance of the diecushioning means as the ram descends on its forming stroke. The pusherposts 21 preferably are in the form of rigid sleeves Z2 fixedly mountedon plates 23 which, in turn, are xedly secured on the ram or die bysuitable bolts 24. Rods 25 are mounted in the sleeves 22 in telescopicrelation and for adjustment endwise therein. Preferably, adjustment isprovided by complementary threads on the interior of the sleeves and onthe exterior of the rods 25, with a suitable lock nut as for locking therods 2-5 in the adjusted position.

By virtue of this adjustment, the elevator can be moved downwardly in apreselected relation to the closure of the dies.

Mounted on the elevator l2. are tensioning means for applying tension tothe stock. The tensioning means include gripping heads arranged in a rowand transversely of the elevator and mounted thereon for movement in adirection toward and away from the dies in a generally horizontal pathtransversely of the path of the ram.

In the form illustrated, the heads are mounted on a slide frame orcarriage 3t? havins a top frame portion 31 and a lower frame portion 32. The top frame portion comprises a bottom plate 33 and a top plate 34with suitable upright tie plates 35 disposed thereoetween andpermanently fixed thereto. This divides the top portion into a pluralityof open end compartments 36 in each of which is mounted a suitablegripping head.

Each gripping head comprises a lower jaw 38 rigid with the bottom plate33, an upper movable jaw 39 connected to the upper plate 34 so as toswing toward and away from the die. A suitable connection is provided bymeans of a ball and socket joint, including a ball 4t? engaged in asocket 41 in the upper frame member. The jaws have cooperating gripping=faces 42 and 43 so arranged that when the jaw 39 is moved toward thedies, the metal stock, indicated at S, can be gripped at its margintherebetween. Preferably, the jaws are one set of jaws common to theentire row of heads, but they may be separate sets of jaws for each ead,if desired.

in order to operate the jaws for opening and closing them, the movablejaw 39 is connected to a suitable piston and cylinder assemblage bymeans of a clevis secured to a rod 45 of a piston 47' which isreciprocable in a cylinder which may be operated by an air or hydraulicpressure in a conventional manner under the control of a suitablereversing valve. if desired, the cylinder may be of the spring returnedtype. The cylinder 48 is connected to a suitable bracket &9 by means ofa horizontal pivot 5t and the bracket '49 is connected to the plate ormember 3i? in fixed position thereon. The lower portion 32 of thecarriage comprises a plate 53 from which is suspended a solid metal bodymember 54. The body member is provided with a plurality of cylinderbores 55' arranged in a row parallel to the gripping jaws and with theirantes extending generally horizontally toward and away from the dies, orthe mid-portion of the bed 2.

Mounted within each cylinder 55 is a piston 56 having a piston rod 5'7which is connected in fixed position by a suitable bolt or other means58 to the elevator 12, as best illustrated in FIG. 4. A suitable packinggland S9 with a compression ring llis provided for sealing the cylinder55 with a slide fit about the rod 57. A suitable packing gland 61secured by a compression plate 62 is provided for sealing the oppositeend of each cylinder 55.

For supplying pressure fluid to, and venting the cylinder at the headend of the piston, a pipe is threadedly connected to the compressionplate 6.2 and, in turn, is connected to a suitable flexible hose leadingthrough a reversing control valve to a source of fluid under pressure.The pipe 63 extends through a suitable passage 65 in the elevator formovement axially relative to the elevator.

For supplying pressure to and venting the rod end of the cylinder, asuitable pipe 66 is provided and is connected at one end to a flexiblehose 67 by which it is connected, in turn, to the reversing controlvalve. The pipe 66 is connected to the cylinder at a position such thatit is just to the left of the piston in FIG. 4, when the carriage ismoved to its closest position to the die.

The piston rod 57 is made of large diameter so that only a small amountof ilui-d need be supplied to the rod end of the cylinder for clfectirna rapid return of the carriage to starting position adjacent the die.

Pressure fluid is supplied from a suitable pump 69 driven by a motor 7%through the reversing valve '71. The reversing valve 71 may be a remotecontrol valve, if desired. It is arranged not only to reverse thepressure but, in an intermediate position, to seal both ends of thecylinders 55 so as to lock the carriage in a fixed position in event itis desired to apply stretch forming tension to one end of the stock byone of the carriages only While using the other as a mere anchor for theother end of the stock.

With the arrangement desired, the fixtures can be mounted between theupright end frame members of the press at the ends of the dies withoutin any Way changing the operating mechanisms of the press and withoutmaking complicated connections between the fixture and the pressoperating parts. By virtue of the lift rods Ztl on the elevators, thestretch forming heads can be lifted to a position where they can gripthe opposite margins of the stock at the ends of the dies while thestock is between and in spaced relation to both dies, and can apply thestretch forming tension thereto by operating the pistons so for movingeither 'or both the carriages relative to the associated elevators.

In order to insure that the frames 11 retain their positions in spacedrelation to each other endwise of the die, suitable connections are madetherebetween. In the form illustrated, the connections include sleeves74 rigidly secured to the stationary frames '11 and turnbuckle bolts 75threadedly engaged with the sleeves 74, respectively, so that the framesIi can be drawn toward or pushed away from each other and held rigidlyin the position to which they have been moved.

By virtue of this connection, the stationary frames can be adjusted fora suitable distance endwise of the bed and locked in position, ifdesired. When so moved, the lift rods 29 are passed through differentsets of holes conventionally provided in the bed 2,.

Suitable downstops 77 are mounted on the stationary frames in positionto engage the underside of the elevator and limit its downward movementin a position in which the pipe 66 is clear of the bottom of thestationary frame it is apparent that with these fixtures fastened ontothe bed or the press, the stock can be tensioned to the degree desiredpreparatory to the closure of the die. While held under the tension, theelevators can be moved downwardly in the desired relation to the downwarmovement of the ram so that the die closure and position of thestretched stock can be related as desired. Thus the stock can be laidover the lower male die 6 before or during die closure. Usually, themargins gripped by the jaws or gripping heads are at a level at least aslow as, and preferably somewhat below, the level of the correspondingmargins of the male die when the dies begin closing. The exact positiondepends upon the shape of the part and is regulated by adjustment of thepush rods 25.

Having thus described my invention, I claim:

A drawing press including a horizontal die bed, upright guide framemembers at the ends of the bed, respectively, a power driven ram mountedon, and guided by, the guide members for reciprocation in an uprightpath toward and away from said bed, complementary male and femaledrawing dies defining, when closed, a concavo-convex pattern, one :diebeing mounted on the ram for movement in opposite directions therebyparallel to the closed position of the one die, and the other die beingmounted in fixed position on the bed, stretch units arranged at oppositeends of the dies and said units including gripping heads, respectively,operable to engage and grip opposite margins of a length of sheet metalstock, respectively, for applying tension thereto endwise of the rampreparatory to, and during, drawing of the stock by cooperation of thedies, at least one unit comprising an elevator movable upwardly anddownwardly relative to the bed, power means to move the elevatorupwardly and downwardly in pre-selected relation to closure of the dies,a carriage supported on the elevator for movement relative thereto alonga generally horizontal path endwise of the ram toward and away from thedies, co-actin'g means on the carriage and elevator guiding the carriagefor movement relative to the elevator along said generally horizontalpath, the gripping head of said one unit being mounted on the carriagefor movement therewith, and a piston and cylinder assemblage meansdrivingly interconnecting the carriage and elevator for moving thecarriage along said horizontal path relative to the elevator forapplying yieldable tension to the stock for stretching the stock.

References Cited in the file of this patent UNITED STATES PATENTS

